1. Field of the Invention
The present invention relates to image stabilizing systems having shake correcting units for correcting image shake caused by, for example, hand motion, and to optical apparatuses equipped with such image stabilizing systems.
2. Description of the Related Art
In recent cameras, the basic operations involved in performing a photographing operation, such as exposure setting and focusing, are completely automated. Therefore, even those unaccustomed to operating cameras are less likely to fail in taking a picture. Furthermore, in recent years, there has been researched a system for preventing image shake caused by hand motion. For these reasons, the user rarely fails in taking a satisfactory picture.
Such an image-shake preventing system will be described briefly below.
Hand motion occurring when taking a picture with a camera is normally a vibration with a frequency of 1 Hz to 10 Hz. When hand motion occurs at the point of releasing of the shutter, the picture to be taken is prevented from blurring basically by detecting the vibration of the camera caused by the hand motion, and then shifting a correction lens in accordance with the detected value. Consequently, in order to take a picture without blurring even in the case of camera shake, it is necessary to accurately detect the vibration of the camera and to accurately compensate for the displacement of the light axis caused by the hand motion.
The detection of vibration (camera shake) is basically achieved by equipping the camera with a vibration detector. Specifically, a vibration detector detects, for example, an acceleration, angular acceleration, angular velocity, and angular displacement and appropriately implements arithmetic processing on the output values to compensate for the camera shake. On the basis of the detected information, a shake correcting unit is driven to decenter the shooting light axis, thereby reducing image shake.
FIG. 9A is a plan view of a single-lens reflex camera, and FIG. 9B is a side view of the camera.
This single-lens reflex camera has an interchangeable lens 80 attached thereto, which is equipped with an image stabilizing system. The image stabilizing system corrects image shake occurring from pitch shake and yaw shake of the camera, indicated with respective arrows 82p and 82y, with respect to a light axis 81. A camera body 83 has a release member 83a, a mode dial 83b (including a main switch), a retractable strobe 83c, and a camera central processing unit (CPU) 83d. 
In FIGS. 9A and 9B, reference numeral 84 denotes an image pickup element, and reference numeral 85 denotes a shake correcting mechanism that corrects image shake in the direction of the arrows 82p and 82y by freely driving a correction lens 86 in directions indicated by arrows 85p and 85y. Reference numerals 86p and 86y denote angular velocity meters that detect shake occurring in the directions of the arrows 82p and 82y. Arrows 86pa and 86ya indicate detection sensitivity directions. Output signals from the angular velocity meters 86p and 86y are arithmetically processed at the CPU 87 and are converted to target shake-correction values for the shake correcting mechanism 85.
In synchronization with half pressing of the release member 83a provided on the camera body 83 (which is performed for instructing photometry and focusing to prepare for a photographing operation), the target shake-correction values are input to a coil of the shake correcting mechanism 85 via a driving unit 88. Subsequently, an image-shake correcting operation begins.
In the image stabilizing system described with reference to FIGS. 9A and 9B, the angular velocity meters 86p and 86y are used for shake detection. The camera body 83 not only receives rotational shake in the directions of the arrows 82p and 82y shown in FIGS. 9A and 9B, but also receives parallel shake indicated by arrows 11pb and 11yb. However, in normal photographing conditions, the rotational shake in the directions of the arrows 82p and 82y has much more effect on the image than the parallel shake in the directions of the arrows 11pb and 11yb, since the effect of the parallel shake is small. For this reason, only the angular velocity meters 86p and 86y are required for the shake detection.
However, when a photographing operation is implemented at close range (i.e. a photographing condition with high shooting magnification), the effect the parallel shake in the directions of the arrows 11pb and 11yb (which will be referred to as “shift shake” hereinafter) has on the image is not negligible. For example, when an object is to be photographed at close range of about 20 cm, as in macro photography, or when the focal length of a photographic optical system is extremely large (such as 400 mm) and an object is positioned about 1 m from the camera, it becomes necessary to actively detect shift shake and to drive a shake correcting device.
Japanese Patent Laid-Open No. 7-225405 discloses a technology in which an accelerometer for detecting an acceleration is provided so as to detect shift shake on the basis of the detected acceleration. A shake correcting device is driven on the basis of the detected shift shake and an output value from a separately provided angular velocity meter.
As disclosed in Japanese Patent Laid-Open No. 7-225405, the necessity of shift shake correction depends on the shooting magnification. The shooting magnification is generally determined from, for example, how much a lens unit is extended when focused on an object. In other words, a shift shake cannot be corrected until the camera is focused on the object. However, in the case of a large hand motion, the focus precision becomes deteriorated. This not only makes it difficult to attain satisfactory focus precision, but also leads to lower accuracy for calculating the amount of shift shake on the basis of the necessity of the shift shake correction and the shooting magnification.